In order to be effective in hair fixative compositions such as aerosol or nonaerosol hair sprays, mousses and lotions, the film forming resins utilized therein, as well as the films formed therefrom, must meet certain requirements. The resins used in such compositions should be soluble in the solvent systems used to prepare the hair fixative compositions. Particularly in hair fixative compositions containing low levels of volatile organic compounds (VOC), where water is used as the primary solvent, the resin should be water-soluble in order to prepare aqueous solutions of the resins. The resins also must be compatible with the solvent/propellant system in the aerosol applications in order to provide the aerosol fixatives with adequate spray properties. In addition, the films cast from such compositions must be either water-soluble or water-dispersible in order to facilitate the easy removal from the user's hair.
One class of resins used in hair fixatives are acrylic polymers which contain carboxylic acid groups. Exemplary of such acrylic polymer resins containing carboxylic acid groups include without limitation the copolymers of n-tert-octylacrylamide, methyl methacrylate, hydroxypropyl methacrylate, acrylic acid and t-butyl aminoethyl methacrylate, available from National Starch and Chemical Company under the Amphomer and the Amphomer LV-71 trade names; copolymers of n-tertoctylacrylamide, methyl methacrylate, acrylic acid and t-butyl aminoethyl methacrylate, available from National Starch and Chemical Company under the Lovocryl trade name; and copolymers of vinyl acetate, crotonic acid and a vinyl ester of an alpha-branched saturated aliphatic monocarboxylic acid containing from 5 to 10 carbon atoms in the carboxylic acid moiety, available from National Starch and Chemical Company under the Resyn trade name.
Such acrylic copolymers are known to be soluble in organic solvents such as ethanol and, thus, typically are used in hair fixative compositions which utilize an organic solvent as the sole or primary solvent. Such acrylic polymers, it is suggested, are known not to be water-soluble unless their carboxylic acid groups are neutralized by alkaline reagents to a level of at least 90% on a molar basis. If the neutralization on a molar basis is lower than 90%, the films derived from those hair fixative compositions utilizing the acrylic polymers generally should not be water-soluble and the fixative resins should not be removable readily from the hair. Accordingly, if such acrylic polymers are intended to be used in formulating low VOC hair fixative compositions, it is taught generally to neutralize the carboxylic acid content to at least 90 mole percent to enhance the water-solubility of the resin and to ensure the easy removal of the resin from the hair. For example, in International Publication No. WO/93/09757, in hair fixative compositions containing water as the primary solvent and a propellant, 100 mole percent of the carboxylic functionality on the acrylic polymers are neutralized.
In addition to being removable readily from the hair, the resin also must be compatible with the solvent/propellant system. The general water-insolubility of such acrylic polymers creates specific problems with respect to hair fixative compositions which contain water as the sole or primary solvent and a propellant, under pressure, such as low VOC aerosol sprays. In such aerosol hair spray applications, a uniform, fine mist or spray is desirable to effectively distribute the hair fixative on the hair. The high levels of neutralization required to provide solubility of the resin in water and thereby removability of the film from hair, results in increased viscosity of the hair fixative compositions. The high viscosity results in undesirable spray aesthetics, such as a narrow spray cone, large spray droplets, spitting, foaming and forceful spray, for example. Therefore, as indicated above, the carboxylic acid functionality of the acrylic polymers are neutralized prior to their incorporation into such low VOC hair fixatives, generally at a level from 90% to 100% on a molar basis.
Neutralization methods are generally known where such acrylic polymers are neutralized prior to be used in hair fixative compositions. Particularly, U.S. Pat. No. 3,927,199 discloses hair fixative compositions containing acrylic copolymers and organic solvent as the primary solvent. In order to meet the removability requirement of a hair fixative, the acrylic resins may be partially neutralized prior to their being incorporated into the hair fixing formulations, thus permitting them to be removed from the hair merely be rinsing with water. The neutralization may be accomplished by reacting the polymer in the form of a solution in an organic solvent, with or without added water, with a concentration of an alkaline reagent (neutralizing agent) which is equivalent on a molar basis to a minimum of about 50% of the available carboxyl groups present on the polymer. The above method can be conducted in the presence of organic solvents such as ethanol. Methods of neutralizing the acrylic polymer in water as the primary solvent are not disclosed or discussed.
U.S. Pat. No. 4,315,910 discloses acrylic polymers for use in aerosol hair fixatives. Small amounts of water, i.e., 1 to 15%, preferably 3 to 8%, are taught to improve the shelf stability and solubility of the polymer. The carboxylic acid groups of the copolymer require neutralization to enhance the water-solubility of the resin to ensure the easy removal of the resin from the hair. The neutralization of acrylic polymers is accomplished by first reacting a solution of the polymer in an organic solvent, with or without added water, with a concentration of an alkaline reagent which is effective to neutralize 70 to 100 mole percent of the carboxyl groups. The appropriate amount of water (not to exceed 15% w/w) is added then to the organic solvent solution of the neutralized resin prior to charging the formulation into the aerosol container. The propellant used in the aerosol applications is a hydrocarbon or carbon dioxide.
U.S. Pat. No. 4,261,972 discloses pressurized hair spray compositions which may contain a broad range of acrylic resin hair fixatives and from 2 to 30% by weight of water. The acid groups of the acrylic resins are neutralized from 50 to 100 percent with an organic base. When the water content is above 30%, the product is dispensed as a foam, which is not desired. The propellants used in these aerosol applications are hydrocarbons.
There has been an ongoing effort in the hair care industry to significantly reduce or eliminate organic solvents in hair fixatives. Additionally, regulatory bodies push to lower the level of VOC, which include ethanol and equivalent hair fixative solvents, in various industries, including hair care products. As the art suggests, increased levels of water, i.e., up to 30 weight percent, are sought to correct certain deficiencies of organic solvent systems, such as flammability and plasticization.
While the methods of neutralization noted above may be used where an organic solvent is the primary or sole solvent, neutralization where water is the primary or sole solvent used to prepare the hair fixatives is problematic. In the known methods, the dry acrylic polymer is dissolved in the organic solvent prior to being incorporated into the hair fixative, which may include small amounts of water blended therein. However, where water is the primary solvent, one must first determine how to dissolve the water-insoluble, unneutralized polymer in the water solvent. Thus, methods of preparing hair fixative compositions which significantly reduce or eliminate organic solvents in the hair fixative compositions are sought.
The present invention provides such methods for preparing low VOC, acrylic hair fixative compositions, which methods significantly reduce or eliminate organic solvents from methods for making the hair fixatives and the hair fixatives produced therefrom.